The High Plains: You know ’em when you see ’em.
Comparing the seven maps that follow shows the challenge of defining the Great Plains. The first map is the most vague; the last map, the most specific. Using different criteria, each map locates the region’s boundaries differently, especially its soft eastern margin that merges into the lower Central Plains and tall grass prairie.
Visit the U.S.G.S. site http://tapestry.usgs.gov/physiogr/physio.html for a remarkable topographic map of and map key to the physiographic regions of the United States. Geologically, the High Plains, as the term suggests, are composed of numerous layers of relatively horizontal sedimentary rock that slopes gently east from the Rockies toward the Missouri-Mississippi rivers. But erosion has produced complex terrain (geomorphology), especially near larger rivers. Among the landforms on the High Plains are plateaus, mesas, buttes, hogbacks, bluffs, badlands, loess formations, moraines left by continental glaciers, and driftless plains that largely escaped glaciation. Depending on where one puts the boundaries of the region, elevations range from 7,000 feet in Colorado (the Black Forest) to under 1,000 feet in North Dakota (along the Red River) and Texas (Edwards Plateau).
A consortium of scholars at the University of Michigan, Colorado State University, and University of Saskatchewan has defined the eastern boundary of the Great Plains with a concession: “The only agreement on this boundary is that no authoritative line exists. Numerous people have attempted to define this border in both physiographical and cultural terms, using such demarcators as the 100th, 98th, 95th, and 88th meridians; the Missouri, Arkansas, and Mississippi rivers; and various levels of annual rainfall. Our boundaries depend on a combination of climatic, topographical, political, and cartographic criteria, and are ultimately drawn along county borders. According to these definitions, the Great Plains region contains about 475 counties in twelve states.”
As land use maps suggest, the Great Plains have the lowest population density east of the Rockies; in many places fewer than 2 inhabitants per square mile live there. One keenly experiences the loneliness of the land in eastern Montana, eastern Wyoming, and the western Dakotas in the U.S., and great stretches of Alberta and Saskatchewan in Canada. Their rural feel contrasts with significant cities around the perimeter of the Great Plains that serve as the region’s entrepots: Fort Worth, Oklahoma City, Tulsa, Kansas City, Omaha, Sioux Falls, Fargo, Winnipeg, Saskatoon, Edmonton, Calgary, Cheyenne, Fort Collins, Greeley, Boulder, Denver, Colorado Springs, Pueblo, San Antonio, Austin, and Waco. There are also significant cities within the Great Plains, but on average they are smaller than the perimeter cities. The interior cities include Moose Jaw, Regina, Billings, Minot, Bismarck, Rapid City, Pierre, Lincoln, Wichita, Abilene (Kansas), Topeka, Amarillo, Lubbock, Midland, Odessa, Abilene (Texas), and Roswell.
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This photo-essay is part of a series on Great Plains geography.